An implantable cardioverter-defibrillator (ICD) is a device that detects any life-threatening, rapid heartbeat. If such a heartbeat, called an arrhythmia, occurs, the ICD quickly sends an electrical shock to the heart to change the rhythm back to normal. This is called defibrillation.

An ICD is made of these parts:

• The pulse generator is about the size of a large cookie. It contains a battery and the electrical circuits that read the electrical activity of your heart.
• The electrodes are wires, also called leads, that go through your veins to your heart. They connect your heart to the rest of the device. Your ICD may have 1, 2, or 3 electrodes.
• All ICDs have a built-in pacemaker. Your heart may need pacing if it is beating too slowly or too fast, or if you have had a shock from the ICD.

A surgeon will insert your ICD when you are awake. The area of your chest wall below your collarbone will be numbed with anesthesia, so you will not feel pain. The surgeon will make an incision (cut) through your skin and create space under your skin and muscle for the ICD generator. Usually this space is made near your left shoulder.

Using special x-ray to see inside your chest, the surgeon will place the electrode into a vein, then into your heart. Then the surgeon will connect the electrodes to the pulse generator and pacemaker.

The procedure usually takes 2 to 3 hours.

An implantable cardiac defibrillator is placed in people who are at high risk of sudden cardiac death. Reasons you may be at high risk are:

• You have had life-threatening bouts of ventricular tachycardia (VT) or ventricular fibrillation (VF).
• Your heart is weakened, too large, and does not pump blood very well. This may be from earlier heart attacks, heart failure, or cardiomyopathy (a diseased heart muscle).
• Certain congenital (present at birth) heart problems or genetic health conditions

See also:

• Heart attack
• Heart failure